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From:   Wenchao Hao <haowenchao@huawei.com>
Subject: [REQUEST DISCUSS]: speed up SCSI error handle for host with massive
 devices
To:     <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Mike Christie <michael.christie@oracle.com>,
        Lee Duncan <lduncan@suse.com>
CC:     Wu Bo <wubo40@huawei.com>, Feilong Lin <linfeilong@huawei.com>,
        <zhangjian013@huawei.com>
Message-ID: <71e09bb4-ff0a-23fe-38b4-fe6425670efa@huawei.com>
Date:   Tue, 29 Mar 2022 17:06:30 +0800
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SCSI timeout would call scsi_eh_scmd_add() on some conditions, host 
would be set
to SHOST_RECOVERY state. Once host enter SHOST_RECOVERY, IOs submitted 
to all
devices in this host would not succeed until the scsi_error_handler() 
finished.
The scsi_error_handler() might takes long time to be done, it's 
unbearable when
host has massive devices.

I want to ask is anyone applying another error handler flow to address this
phenomenon?

I think we can move some operations(like scsi get sense, scsi send startunit
and scsi device reset) out of scsi_unjam_host(), to perform these operations
without setting host to SHOST_RECOVERY? It would reduce the time of 
block the
whole host.

Waiting for your discussion.